fMRI and Ghrelin in Obesity and Binge Eating Disorder

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DESCRIPTION (provided by applicant): The prevalence of obesity continues to increase in the US and globally. Obesity results in increased morbidity and mortality, especially from diabetes and heart disease. Approximately 30% of obese individuals seeking treatment have binge eating disorder (BED). They ingest very large meals without purging afterwards as in bulimia nervosa. BED, the most common characterized eating disorder, causes much distress and contributes to the development of obesity. Although psychological factors have been studied, little is known about the biological factors of BED. This clinical research study will focus on brain imaging and gut hormones following a meal to examine differences between BED and non-BED subjects. There will be 24 obese BED (12 m, 12 f) and 24 weight-matched obese non-BED (12 m, 12 f) subjects. On one day, a fixed liquid meal (750 ml) will be ingested and blood drawn to measure various appetite hormones including ghrelin, PYY, and GLP-1, measured before and during a 2-hour period afterwards. The prediction is a lower fasting level of ghrelin and a smaller postprandial fall in BED compared to non-BED subjects. Also predicted are lower fasting levels and smaller postprandial increases of PYY and GLP-1 in BED compared to non-BED subjects. On another day, only water (750 ml) will be ingested as a control for diurnal variation in these hormones. At 135 min after the fixed meal or water, functional imaging (fMRI) will be employed to examine brain activation areas in response to visual and auditory stimuli of binge foods, nonbinge foods, and nonfoods. Greater activation is expected in such areas as the prefrontal cortex in response to binge foods relative to the other stimuli groups in BED than in nonBED subjects. Increased activation is also expected to binge food stimuli in the BED subjects even in the fed state as binge eating often occurs in the absence of hunger. On a third day, various psychological scales to assess eating behavior and mood will be administered. Body composition will be measured to obtain percentage body fat to verify similar body composition in the two groups. This study on brain imaging and meal-related appetite hormones should improve our knowledge of the underlying biological factors in Binge Eating Disorder (BED). This may lead to improved diagnosis and treatments to help restore normal appetite hormone levels and brain activity in BED, a disorder which is increasing in prevalence alongside obesity.